US Bridges

SB Ia 1 over Ralston Creek

Fair

Johnson County, Iowa · 2.5 Mi. S of Jct. I-80 · Structure no. 000000000031750

Built
1953
72 years old
Condition
Fair
inspected June 2024
Type
Frame
Concrete
Length
56 ft
1 main span
Daily traffic
3,650
2022 count
Owner
State
State Highway Agency

About this bridge

SB Ia 1 over Ralston Creek is a concrete frame carrying SB Ia 1 over Ralston Creek in Johnson County, Iowa. It was built in 1953, so it is 72 years old, older than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 3,650 vehicles a day, roughly 2% of them trucks, projected to reach 3,650 by 2044. The structure is 56 ft (17.1 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesSB Ia 1
CrossesRalston Creek
Location2.5 Mi. S of Jct. I-80
RouteState Highway 1
CountyJohnson County
StateIowa
Coordinates41.66067, -91.52576
Functional classUrban Other Principal Arterial

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating48.6 US tons
Inventory rating32.7 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length56 ft (17.1 m)
Longest span50 ft (15.2 m)
Deck width43 ft (13.1 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,650 (2022)
Projected traffic3,650 by 2044
Trucks2%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was SB Ia 1 over Ralston Creek built?

It was built in 1953, making it 72 years old in 2025.

What condition is SB Ia 1 over Ralston Creek in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in June 2024.

How much traffic does SB Ia 1 over Ralston Creek carry?

About 3,650 vehicles per day (2022 count), of which roughly 2% are trucks.

How long is SB Ia 1 over Ralston Creek?

The structure is 56 ft (17.1 m) long with a longest span of 50 ft (15.2 m) and a deck 43 ft wide.

Who owns SB Ia 1 over Ralston Creek?

It is owned by the State Highway Agency.